Statistical analysis
The data are expressed as the mean ± standard deviation. ANOVAs in the form of Newman-Keuls tests were used to compare the means of continuous variables among groups, and any significant difference was further analyzed using the Tukey–Kramer test. All of the statistical tests were two-sided, and a probability value <0.05 was required for statistical significance. All of the statistical analysis was performed using SPSS 20.0 software.